1. Field of the Invention
The present invention relates to an efficiency information display for a vehicle and a method for displaying vehicle efficiency information.
2. Background Art
All vehicles, whether passenger or commercial, include a number of gauges, indicators, and various other displays to provide the vehicle operator with information regarding the vehicle and its surroundings. With the advent of new technologies, such as hybrid electric vehicles (HEV's), has come a variety of new gauges and information displays that help drivers to better learn the operation of these vehicles that utilize new technology. For example, many HEV's incorporate gauges that attempt to provide the driver with information on the various hybrid driving states. For example, some gauges will indicate to the driver when the vehicle is being propelled by the engine alone, the motor alone, or a combination of the two. Similarly, a display may indicate when the motor is operating as a generator, and is recharging an energy storage device, such as a battery.
In addition to indicating power flow, some gauges on HEV's indicate an instantaneous fuel economy. Although helpful in some situations, gauges of this type can give a driver a false sense of improved efficiency under certain conditions. For example, during regenerative braking—i.e., braking that results from a negative torque output by an electric motor—a gauge may indicate that the battery is charging and fuel economy is very high. A gauge of this type can lead a driver to believe that more aggressive braking is better since the fuel economy indicator reaches a maximum. In situations where the battery is fully charged, or braking is so aggressive as to initiate friction braking, efficiency is actually reduced; unfortunately, this is not apparent to the driver. In addition, even though an instantaneous fuel economy may be very high, greater efficiency may be able to be achieved if the driver operates the vehicle in a less aggressive manner during both acceleration and deceleration. Thus, merely indicating regenerative braking or instantaneous fuel economy may not provide an accurate picture as to vehicle operating efficiency.
Therefore, a need exists for an efficiency information display for a vehicle, and a method for displaying such information, that provides information independently from an instantaneous fuel economy measurement.